How to build a functional thermometer?

Question

How would you make a FUNCTIONAL thermomter which works in a temperature range of about 10-80 degrees Celsius.

Answer 1

Here's something to try, I think it might work, at least as proof of concept anyway. Get a glass or clear plastic tube with the inside diameter of about 1/16 to 1/8" about a foot long. Get a single drop of water about 1/2 way down the tube (the drop must totally fill the diameter of the tube to work). Now seal one end of the tube. This thermometer relys on the thermal expansion of air to move the drop up and down the tube. You will neet to calibrate the thermometer using a known good thermometer. Make a mark at what will be the "immersion depth" of your thermometer. Note you must immerse the closed end of the tube! It isn't that important the exact length as long as it is 1] several inches, and 2] not quite up to the water drop. Always immerse your thermometer to this same depth when calibrating or measuring. Now place with a good thermometer in water, cool with ice to 15 C, then 10 C then 5 C make a mark where the water drop is for each temp. (You can mark the top. bottom, or middle of the drop as the temp point; just be consistant. Now take some new water with you thermometer and the reference thermometer, and heat to 25 C, 30 C ect up to boiling (100 C). Make your marks of water drop position at each temp. Be careful at the higher temperatures not to get burned! You should be able to measure temperatures with your thermometer (it's not going to be as accurate as a commercial one of course). Be careful not to drop it; the water drop position might change and you will have to re-calibrate. You may need to experiment with different tube materials, lengths etc to get best results.

Answer 2

Take a Pyrex test tube and place it end down in water. Gently heat the tube to water's boiling point (100C). Let this continue for a short time. This gets rid of excess air and creates a slight vacuum. Allow the tube to cool in your refrigerator (about 2C) and mark where the water height ended. Now, the temperatures are marked from 2C at the bottom of the upside down tube to 100C at the top of the tube inside the water. Make even marks on the tube with a ruler, be sure not to take the tube out of the water.

There you go.

Have fun.

Answer 3

A 0-100 C thermometer is going to cost about 20 bucks, why would you want to spend three grand on the equipment and supplied you would need to make one?